Quinaldine catabolism was investigated with the bacterial strain Arthrobacter sp., which is able to grow aerobically in a mineral salt medium with quinaldine as sole source of carbon, nitrogen and energy. The following degradation products of quinaldine were isolated from the culture fluid and identified: 1H-4-oxoquinaldine, N-acetylisatic acid, N-acetylanthranilic acid, anthranilic acid, 3-hydroxy-N-acetylanthranilic acid and catechol. 3-Hydroxy-N-acetylanthranilic acid was not further metabolized by this organism. A degradation pathway is proposed.